The present invention relates to a general-purpose internal combustion engine for use as a prime mover in various machines for agricultural, civil construction, and other uses and in various portable machines such as electric generators and pumps, and more particularly to such a general-purpose internal combustion engine having an air cleaner with a precleaner.
Internal combustion engines for use as prime movers in various machines for agricultural, civil construction, and other uses and in various portable machines such as electric generators and pumps, are often used in dusty places. Therefore, the filters in the air cleaners of such internal combustion engines are liable to get clogged soon, and have to be frequently cleaned or replaced. to avoid this shortcoming, there have been proposed general-purpose internal combustion engines as disclosed in Japanese Utility Model Publication Nos. 27-5504 and 54-20689, for example. The disclosed internal combustion engines have a main air cleaner employing a filter of paper and/or urethane foam and a cyclone-type precleaner positioned laterally of the main air cleaner. Dust-laden air is first introduced into the precleaner which removes most of the dust from the air. The air from the precleaner is then introduced into the main air cleaner through a port defined in a side thereof.
With the conventional air cleaner arrangements, however, the precleaner is simply connected to the air inlet port of the main air cleaner. The prior air cleaner structures have failed to meet the following requirements:
(a) The precleaner should not project out of the assembly of an engine, a fuel tank, a muffler, and an air cleaner, so that the precleaner would not impair the appearance of the engine assembly, would not obstruct the operation of a recoil starter, or would be damaged by being hit by an object;
(b) The precleaner should be located so as not to draw air heated by a heating body such as a muffler;
(c) The main air cleaner and the precleaner should should be interconnected by a joint duct having a small resistance to the flow of air therethrough;
(d) The precleaner should be structured so that it could easily be formed;
(e) The precleaner should be arranged so that dust discharged therefrom would not be drawn through its own air inlet port into the precleaner; and
(f) The joint between the precleaner and the main air cleaner should be durable.
The filter of the main air cleaner is oval or generally cylindrical in shape and housed centrally coaxially in an air cleaner case having a complementary shape. The filtered air discharged from the precleaner is introduced into the main air cleaner case toward the vertical axis thereof and impinges substantially perpendicularly upon the outer circumferential surface of the oval or cylindrical filter, with the result that the filter portion hit by the filtered air tends to get clogged soon. Therefore, the entire circumferential surface of the filter is not effectively utilized, and it is uneconomical to clean or replace the entire filter when the other filter portion is not appreciably clogged.
The present invention has been made in an attempt to meet the aforesaid requirements of the general-purpose internal combustion engines and also to solve the above problem of the conventional air cleaner combined with the cyclone-type precleaner.